-- =============================================================================================================== -- InductionController in tray allocation for a sortation system -- By José Antonio Esparza and Kim Bjerge - spring 2010 -- ===============================================================================================================
class InductionController types
values public InductionRate : nat = 2; -- trays between each item
instancevariables
priority : nat := 0; -- priotity of induction, incremented each time wait to induct item
id : nat1; -- Induction ID
allocator : TrayAllocator; -- TrayAllocator
items : seqof Item := []; -- set of items ready to be inducted
stepCount: nat := 0; -- Counts the number of steps between inducting items
-- If induction is waiting there must be items in sequence inv priority > 0 => len items > 0;
-- Returns induction controller UID
pure public GetId: () ==> nat
GetId() == return id;
-- Returns priority of induction controller public GetPriority: () ==> nat
GetPriority() == return priority;
-- Returns true if induction is wating with an item public IsItemWaiting: () ==> bool
IsItemWaiting() == return priority > 0;
-- Get size of waiting item in number of trays public GetSizeOfWaitingItem: () ==> nat
GetSizeOfWaitingItem() == ifnot IsItemWaiting() then return 0 -- No waiting items else let item = hd items in item.GetSizeOfTrays();
-- Enviroment feeds a new item on induction public FeedItem: Item ==> ()
FeedItem(i) ==
items := items ^ [i];
-- Simulate sorter-ring moved one tray step public TrayStep: () ==> ()
TrayStep() ==
( -- Induct next item based on InductionRate
stepCount := stepCount + 1; if IsItemWaiting() or (stepCount >= InductionRate) then
(
InductNextItem();
stepCount := 0;
)
);
-- It any items on induction then induct next item -- If next item could be inducted then removed it from the head of item sequence -- If item could not be inducted then increment priority private InductNextItem: () ==> ()
InductNextItem() == let n = len items in if n > 0 then let item = hd items in if allocator.InductItem(self, item) then
( atomic-- Due to invariant
(
items := tl items;
priority := 0
);
) else
priority := priority + 1; -- Increment priority wait counter
functions
sync
--thread
traces
end InductionController
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